2 citations · 2 across the 5 of their papers we have counts for
5 papers
A Toeplitz-like operator with rational matrix symbol having poles on the unit circle: Invertibility and Riccati equations
G. J. Groenewald, S. ter Horst, J. Jaftha +1
This paper is a continuation of the work on unbounded Toeplitz-like operators $T_\Om$ with rational matrix symbol $\Om$ initiated in Groenewald et. al (Complex Anal. Oper. Theory 1…
A Toeplitz-like operator with rational matrix symbol having poles on the unit circle: Fredholm characteristics
G. J. Groenewald, S. ter Horst, J. J. Jaftha +1
In a recent paper (Groenewald et al.\ {\em Complex Anal.\ Oper.\ Theory} \textbf{15:1} (2021)) we considered an unbounded Toeplitz-like operator generated by a rational matri…
Galois groups and rational solutions of
G. J. Groenewald, G. Goosen, D. B. Janse van Rensburg +2
We extend Theorem 1 of R. Reams, A Galois approach to m-th roots of matrices with rational entries, LAA 258 (1997), 187-194. Let be any polynomial over and let…
Polar decompositions of quaternion matrices in indefinite inner product spaces
G. J. Groenewald, D. B. Janse van Rensburg, A. C. M. Ran +2
Polar decompositions of quaternion matrices with respect to a given indefinite inner product are studied. Necessary and sufficient conditions for the existence of an -polar deco…
Bounded Real Lemma and structured singular value versus diagonal scaling: the free noncommutative setting
Joseph A. Ball, Gilbert J. Groenewald, Sanne ter Horst
The structured singular value was introduced independently by Doyle and Safanov as a tool for analyzing robustness of system stability and performance in the presence of struct…